Switching up certain COVID-19 vaccines may be better than sticking with the same one.
That's according to a major new study from the University of Oxford.
It tested more than 1000 volunteers and found that a first dose of either the AstraZeneca-Oxford or Pfizer-BioNTech vaccines followed by a second dose of Moderna resulted in a strong immune response.
Stronger, even, than if the volunteers had stuck with the same vaccine.
Oxford Vaccine Group's Matthew Snape was lead researcher.
"When it comes to antibodies, it was really the RNA vaccines that seem to be most immunogenic. And if you want to choose between them, then actually, overall, we seem to see that Moderna was more immunogenic than the Pfizer vaccine. That's a high dose of the RNA vaccine in that so perhaps that wasn't surprising."
The study may be good news for developing countries struggling to get access to vaccines.
"We're showing there is flexibility, you don't have to stick rigidly to receiving the same vaccine for a first and second dose,and that if the programme will be delivered more quickly by using multiple vaccines, then it is okay to do so. I think that might be one of the most important findings from this study."
The study comes as pressure grows for speedier vaccination campaigns worldwide as variants like Delta and Omicron spread.
But Snape said the study also has implications for the future.
And could lead to a new, more flexible approach to fighting disease.